The Magnetic Flux Leakage And Ultrasonic Hybrid NDT Method And System Based On Steel Pipe Rotating

Steel pipes are widely used in many industries, and are important for the development ofnational economy and the improvement of human life quality. However, defects such ascracks, folds and corrosion appear during the production and use of the steel pipe, leading toenormous economic losses. So, implementing NDT for steel pipe is necessary. Due to thedrawbacks of each traditional detection method, hybrid NDT methods are commonly used insteel pipe detection in order to realize the fully seeking of defects.This paper researches a magnetic flux leakage (MFL) and ultrasonic hybrid NDT methodbased on steel pipe rotating, and seeks for the methods to ensure the consistency and stabilityof the signal and realize full coverage of steel pipe detection through the study of probescanning trajectory, the kinematic equation and solution of the probe tracking device and theoptimized detection gesture of the probe.Four automatic steel pipe detection systems are analyzed and compared, within whichtwo types of probe scanning trajectory are adopted: the linear and the spiral line type. Thelayout of the probe, the scanning trajectory of the probe with its influence on parameters andthe relationship of the defect location and the signal of each type are studied deeply.Specifically, the formulas and solving methods of screw pitch through the mathematicalmodeling of steel pipe rotation spirally in V-shaped wheel are given. Based on the abovestudies, the necessary and sufficient condition for full coverage of steel pipe detection isfigured out. Then, the kinematic of the probe tracking device and the optimized detectiongesture of the probe are studied. The kinematic equation of the probe tracking device ispresented, and its forward and inverse solution are given. Aiming at reducing the signalinterference and ensuring the consistency and stability of the signal during steel pipeautomated detection, four degree of freedom probe tracking device are designed.Summarizing the result of the research, a suit of MFL and ultrasonic hybrid NDT systembased on steel pipe rotation spirally is developed. The scanning trajectory, the probe trackingdevice and the signal processing and control system are designed in detail. The equipment istested according to the national standard and has a preferable test result. It has beensuccessfully applied in many steel pipe plants.